The invention relates generally to high-capacity Synchronous Optical NETworking (SONET) telecommunications network interconnections and trouble isolation of customer digital signal circuits transported by the network. More specifically, the invention relates to detecting and isolating digital signal circuit problems at a DS3 level embedded in SONET protocol.
Traditional wireline telephone companies are divided into two large categories, long distance (IntereXchange Carrier, or IXC) and local/access (Local Exchange Carrier/Access Provider, or LEC/AP). An IXC carries both voice and data traffic for customers who have access to an IXC network via an LEC/AP. An IXC provides a network made up of a large number of high-capacity links/links that connect to different locations, where LECs/APs have Point of Interfaces (POI) that provide connections to customers for their Customer Premise Equipment (CPE). These links are of varying capacities (T3, OC-3, OC-48, OC-192, etc.) and the traffic in these links use Plesiochronous Digital Hierarchy (PDH) or SONET protocols.
There are major savings for an IXC to buy bulk optical access from an LEC/AP. In most new arrangements, the POI between the IXC and AP is optical and is referred to as an optical POI (OPOI). These OPOIs may carry optical or electrical customer circuits.
To build a facility from a source point A (POI) to a destination point Z (POI) requires access into an IXC network and the ability to route the traffic within this collection of links. The POIs can be either T3 or OC-N. Once an IXC receives traffic into its network at the source point A (POI), the IXC has to route the traffic over a number of different links (the Layer 1 transport network) to have it arrive at the destination point Z (POI). Each link segment that the IXC uses has two ends. The overall path that the traffic negotiates from source A to destination Z is a collection of link segments. Each end of the link segment has a sensor that can detect if traffic is flowing. An inventory of how the traffic flows from source A to destination Z lists all the link segments involved. If one of the links fails and the traffic stops flowing past its sensor, an alarm is sent to a network maintenance (surveillance) system. The network maintenance system identifies the problem link and can sectionalize the problem of the source A to destination Z traffic flow to the failed link segment.
While OPOIs provide reduction in access costs to IXCs, OPOIs do not have the ability to provide Service Assurance (SA) to that IXC's customer care for lower level digital signals, for example, Digital Signal (DSX) circuits which typically terminate on router Channelized Optical Carrier (CHOC) cards.
For DS3 circuits carried in these layouts, SONET/synchronous digital hierarchy (SDH) network elements (NEs) do not provide visibility to the IXCs for DS3 alarms or Performance Monitoring (PM) parameter data. Typically, there are no DS3 alarms available for a pure SONET network with an OPOI.
What is desired is a method that monitors/analyzes SONET and DSX alarms and Performance Monitoring (PM) data, and detects and locates faults on DSX circuits.